1. Field of the Invention
The invention relates to a method for fabricating an aperture, and more particularly, to a method for fabricating an aperture in a hard mask while preventing the occurrence of bowing profile on sidewall of the hard mask where the aperture is being formed.
2. Description of the Prior Art
The trend to micro-miniaturization, or the ability to fabricate semiconductor devices with features smaller than 0.1 micrometers, has presented difficulties when attempting to form narrow diameter, deep (high aspect ratio) contact holes in a dielectric layer, to expose underlying conductive regions.
Conventional approach of fabricating contact holes typically involves first providing a semiconductor substrate with a plurality of semiconductor devices thereon, in which the semiconductor devices includes MOS transistors or resistors. At least a dielectric layer and a hard mask are then formed on the semiconductor substrate to cover the semiconductor devices, and a patterned resist is used to perform a series of pattern transfer processes to form a contact hole in the hard mask and the dielectric layer.
However, conventional method typically uses an oxygen containing gas for performing the aforementioned pattern transfer process, which causes severe indentation with respect to the central region of the sidewall and ultimately produces a bowing profile. Unfortunately, metal deposited in the contact hole thereafter is likely to seal the entrance of the hole before filling the expanding bowing portion of the contact hole. As a result, a seam is formed relative to the central region of the deposited metal, which degrades the electrical connection of the device and affects the overall performance.